An anchor device or an anchor (also referred to as a wall plug) is a component that is used in fastening technology and that is employed in various materials into which a screw cannot be directly screwed, unlike, for example, a wood screw into wood. The anchor is inserted as an intermediate part into a cylindrical hole in walls, ceilings or floors that are usually made of masonry or concrete or that are fitted with panels. Upon being screwed in, the wood screw or particle-board screw expands the anchor, thereby creating a positive fit—and to a lesser extent sometimes also a non-positive fit—between the anchor and the material surrounding it so that the anchor cannot be pulled out. A drill with hard-metal cutting edges (concrete drill) is employed to drill the hole in the hard material.
Such a conventional anchor is disclosed, for example, in German utility model DE 201 06 520. The anchor shown in this document of the state of the art has an expansion section that extends axially over part of the length of the anchor. This expansion section is expanded when an expansion screw is screwed into the anchor. The expanded and deformed anchor creates a positive connection between the screw and the wall of the drilled hole into which the anchor and subsequently the screw have been inserted. Owing to this positive connection between the screw that has been screwed into the anchor and the wall of the drilled hole, a high level of static friction is generated that holds the screw inside the drilled hole.